Field of the Invention
The present invention relates to a pumping unit, and in particular, to a derrick-type long-stroke hydraulic pumping unit.
Description of Related Art
A pumping unit is a machine device for oil extraction and is known as a “nodding machine”, which pumps petroleum out of a well through pressurization. At present, a “triplex” (a sucker pump, a sucker rod, and a pumping unit) manner is commonly used for oil extraction in oil fields. In existing derrick-type long-stroke hydraulic pumping units, a rack of a hydraulic pumping unit is of an oblique ladder shape, which in one hand results in waste in materials, and in the other hand has low firmness, is inconvenient to maintain, and cannot satisfy use requirements. The existing hydraulic pumping unit has a complex hydraulic control system, which has high technical requirements for use and maintenance and cannot satisfy production and energy-saving requirements of an end user. The existing pumping unit has an oil cylinder structure having the disadvantages of a complex structure, low work efficiency, and poor sealing, and a shell of the cylinder is easily worn after the cylinder is used for a long time, thereby affecting its work efficiency and service life. Furthermore, when the hydraulic pumping unit is maintained, a counterweight basket or an oil cylinder needs to fall onto the ground or the lowest position, and after the maintenance is finished, the counterweight basket or the oil cylinder needs to be restored to its original position and provided with a load. However, the counterweight basket or the oil cylinder is very heavy so that it is very difficult to restore the counterweight basket or the oil cylinder to the original position. Therefore, there is a need for an improved technique to solve the problems in the prior art.